While I was spending much of my free time playing MechWarrior 5: Mercenaries, I still worked on my usual project ideas. I just wasn't writing them down on this blog! I am already starting to forget important details so I'll try to catch up the best I can. First up for documentation: the spent spool storage system project.

Everyone using 3D printing to turn ideas into reality will quickly collect a number of spent filament spools. They are intended to be thrown away into landfill, and many do, but every time I hold an empty spool in my hand I wish I had some way to repurpose it. I've seen published projects turning a spent spool into a storage tray. (Here is one of many examples.) This is a neat idea, but I feel there's room for me to offer some meaningful improvements.

The biggest problem with existing solutions is that they are fixed in size. Spool dimensions are not all identical. From my experience spools for one kilogram of filament have some typical dimensions. They usually have an outside diameter of 20cm and a center hole of 5.5cm, with small variations on each value. However, the actual inner diameter of the filament spool area varies a lot more. For the sake of reducing curvature of filament (to make it easier to feed into a printer) the inner spool is usually several centimeters larger than center hole diameter. To accommodate the same amount of filament wound around a larger inner diameter, the thickness of the spool may increase. Different manufacturers make different diameter/thickness tradeoffs.

As a result, STL files published online would fit one specific size of filament spool but would not fit one with different inner diameter or thickness. What we need is a design that can be configured to fit different spool dimensions. There are several configurable OpenSCAD scripts out there, but I'm going to take this as an opportunity to practice CadQuery which will also allow such configurability.

Another disadvantage of published STL is that the storage bin size is fixed. Some of the published designs include small partitions to subdivide a bin, but I've used small partitions in commercial storage bins and they tend to slide out of place making a mess. What I really want is to have custom configurable storage bin sizes, and again CadQuery can make the idea practical.

Unrelated to fixed nature of STL, I wanted to reduce filament usage. The storage systems I've seen online are built to be sturdy, but I felt they tend to go overboard and use wasteful amounts of filament to accomplish their goal. I'm not trying to store gold bars here! I'm willing to go with lighter construction in order to reduce filament usage.

With these goals in mind, I started by experimenting with storage tray designs.

Source code for this project is publicly available at https://github.com/Roger-random/r2s4